Heat treating furnaces



Aug. l1, 1964 J. E. MARTIN HEAT TREATING FuRNAcEs 4 Sheets-Sheet l Filed0G11. 5, 1961 EN Tof?- ron/ver Aug. 11, 1964 J. l;` MARTIN HEAT TREATINGFuRNA-cEs 4 Sheets-Sheet 2 Filed OGt. 5, 1961 NVEIVTOI? ATTORNEY FIG.

Aug. 11, 1964 J, E. MARTIN HEAT TREATING FURNACES 4 Sheets-Sheet 3 FiledOct. 5, 1961 A T TOHNE'Y Aug. 11, 1964 J. E. MARTIN HEAT TREATINGFURNACES 4 Sheets-Sheet 4 Filed Oct. 5, 1961 "MIMI" ATTRNEY UnitedStates Patent O 3,144,245 HEAT TREATING FURNACES Joseph E. Martin, 19255John R, Detroit, Mich. Fitted Get, 5, 1961, Ser. No. 143,080 8 Claims.(Cl. 26S- 34) The present invention relates to improvements in retortfurnaces, and more particularly to a heat treating furnace in which theretort is oscillated about its longitudinal axis to tumble theworkpieces, and is reciprocated longitudinally to convey the workpiecesthrough the furnace retort.

One object is to provide a retort furnace in which the retort isreciprocated to effect feeding of the workpieces and is provided withindependent means for oscillating the retort about its axis, whereby theworkpieces may be subjected to various periods of tumbling and differentrates of feed while in the furnace.

Another object is to provide a heat treating furnace of the rotaryretort type having separate and independent feed and tumbling means andthus insure proper heat treating of various workpieces by carburizing,carbonitriding and clean hardening of small workpieces and reducedsection.

Another object is to provide a heat treating furnace in which the retortis mounted on a reciprocating frame and supported within the furnacecasing in such a manner that the retort is reciprocated and oscillatedsimultaneously relative to the casing so that the workpieces will besubjected to the same degree of heat and exposed to the carburizingatmosphere throughout their entire surface with the result that thedepth of hardening will be uniform through the different sections of theworkpiece.

Another object is to provide a heat treating furnace of the retort typehaving a discharge gate which is arranged to normally retard dischargeof the workpieces from the retort to the quenching tank and which may bedisplaced 180 to cause the workpieces to be discharged upon continuedoperation of the reciprocating shuffle mechanism.

Another object is to provide a retort furnace in which sealing membersare yieldingly urged into engagement with the ends of the retort toprovide an effective end seal and providing inlet and discharge memberscoupled with the retort by a butt sealing joint so that the members movelongitudinally with the retort, but remain xed against rotation duringoscillation or rotary to and fr movement of the retort.

Another object is to provide a continuous rotary type retort furnacewhich is capable of being adjusted for batch operation wherein thefurnace is loaded and subsequently discharged simultaneously in batchfashion, or which can be operated continuously and can be fed by ametering type feeder with the workpieces discharged into a quenchingtank where they are removed by an endless buckettype conveyor.

Another object is to provide a retort furnace for heat treatingworkpieces in which the combined reciprocating and oscillating movementimparted to the retort can be regulated to increase or decrease thetumbling rate as well as the time required for the workpieces to travelthrough the retort from the inlet end to the discharge of the retort.

Another object is to provide a retort furnace for heat treating metalworkpieces so that the depth of hardening will be uniform throughout allsections of the workpiece, and in which the ends of the retort aresealed against the entrance of combustion products by sealing membersformed of wear resisting metal arranged in abutting relation with theretort ends and yieldingly urged into sealing contact therewith duringoperation of the furnace.

Another object is to provide a retort furnace in which the retort isreciprocated and oscillated simultaneously t0 lCe effect a feeding andtumbling action with independent means for reciprocating the retortseparate from the means for oscillating the same about its axis, wherebythe furnace can be regulated to a fine degree in accordance withdifferent techniques of heat treating various workpieces.

Another object is to provide a heat treating furnace in which the retortis rotatably supported on a reciproeating frame having guide rollersengaging trackways on a fixed frame so that the retort may be.`oscillated and reciprocated in the furnace and to provide effectivecontactually engaging sealing members between the retort and housing atthe end portions thereof.

Another object is to provide a variable drive unit for oscillating theretort at dierent frequencies and to provide a separate power drive unitfor reciprocating the retort which is capable of being adjusted to varythe reciprocating rate of the retort independently of the Variableoscillaing drive unit.

Another object is to provide a retort furnace for heat treating metallicworkpieces with means for feeding a predetermined number of workpiecesper minute and thus continuously supply the retort with a uniform numberof workpieces which are traveled and conveyed through the furnace at auniform rate and are tumbled during their passage through the furnace toinsure uniform hardening depths throughout the entire workpiece area.

Another object is to provide a retort heat treating furnace which can beused as a batch-type furnace, or which can be operated continuously byfeeding the workpieces mechanically by means of a feeding deviceincluding a conveyor and rotary dispensing measuring device.

Other objects and advantages of the invention will become apparentduring the course of the following description of the accompanyingdrawings, wherein:

FIGURE 1 is a side elevational view of the retort furnace showing themanner in which the retort is mounted for longitudinal movement withinthe furnace structure.

FIGURES 2 and 2a are longitudinal cross-sectional yviews taken on line2-2 of FIGURE l and looking in the direction of the arrows to illustratevarious structural details.

FIGURE 3 is a vertical cross-sectional view taken on line 3 3 of FIGURE1 and looking in the direction of the discharge end of the furnace andFIGURE 4 is an end elevational view looking in the direction of thedischarge end of the retort furnace.

In the drawings, and more in detail, there is shown a retort-type heattreating furnace structure including a furnace housing generallydesignated 5 and a cylindrical retort generally designated 6 mountedwithin the furnace housing and supported by a reciprocating framestructure generally designated 7.

The retort housing S is supported on a frame structure including spacedrunner-type base bars 8 to the ends of which are Welded or otherwisesecured upright frame bars 9 at each end of the base bars 8.Intermediate the ends of the frame bars 9 there is provided reinforcingangle bars 10 which are welded or otherwise secured in place to formframe bars extending parallel with the base bars 8. Transverse framebars 11 have their ends welded or otherwise secured to the longitudinalframe bars 1t) and the extreme upper ends of the upright frame bars 9are connected by longitudinal frame bars 12 likewise welded or similarlysecured in place.

The retort furnace housing 5 includes a pair of metallic shell sections13 and 14 of semi-circular section with the bottom shell 14 supported bythe spaced apart transverse bars 11 and secured to the longitudinalframe bar 12 by welding or the like. The upperl section 13 is providedon its longitudinal edges with angle bars which are secured to one ofthe flanges of the angle bar 12 by suitable threaded fasteners or bywelding. The shell sections 13 and 14 are provided with refractory brickliner sections 16 and 17 of semi-circular section and are supported byinterposed plate strips 18. The upper section 13 is provided with aburner housing 20 having a portion 22 projecting into openings 23 in thehousing tirebrick liner 17. As shown in FIGURE 1 the burner housings arearranged in spaced apart relation from one end of the housing 5 to theother end, and each burner housing 20 is provided With a fuel supplypipe 24 for feeding a liquid or gaseous fuel to the burner jet cone 26.The burner housings 20 are secured in place by threaded fasteners 27which extend into correspondingly threaded openings in the uppermetallic shell 13 of the housing. The burner supply pipes 24 aresupported in an opening formed in a web 28 in the housing 20 and extendin a direction tangential to the circumference of the furnace housing 5.

Also secured to the upper section 13 of the furnace housing is a pair ofspaced lugs 30 having openings 31 for receiving a hoist sling tofacilitate installation of the furnace by a crane or other hoist, and tofacilitate removal of the upper half of the housing for repairs orreplacement of the lining or retort.

Also supported by the frame structure including the uprights 9 is atrackway 32 of angle section and said trackway is supported by tubularstructural bars 33 (FIG. 4) which have one end welded or otherwisesecured to each upright 9 while the inner ends are Welded or similarlysecured to the webs of the channel bars 32 forming the trackway. Asshown in FIGURE 3 the channel bars 32 are arranged in opposed relationand the ends thereof project beyond the end walls 34 and 35 of thefurnace housing 5. Firebrick structures 36 and 37 are supported by theend walls 34 and 35 similar to the sections 16 and 17.

The ends of the channel bars forming the trackway 32 at one end of theretort furnace are supported on suitable frame bars 40 which are securedthereto by angle plates 41 which are welded or otherwise secured inplace to form braces and additionally support the opposed channelmembers 32.

The carriage for the cylindrical retort is formed by a pair of opposedchannel bars 43 (FIG. 3)which are substantially equal in length to thechannel bars 32 and are connected together throughout their length byspaced transverse channel bars 44 secured in place as by welding atvarious locations. Rotatably mounted on both sides 0f the carriage andsupported by the channel bars 43 is a series of anged wheels 45 whichare mounted on short axle shafts 47. The wheels are received in thetrackway formed by the opposed channel members 32. One end of thecarriage is provided with a base plate 46 and secured to the ends of theopposed channel members 43 at the opposite end as by Welding is a pairof triangular shaped plates 48 to which is attached upright carriagemembers 49. The plate 46 is welded to the flanges of the opposed channelmembers 43 and is similarly provided with a pair of spaced channelmembers 50 connected at their upper ends by a plate 51 suitably securedin place as by welding or threaded fasteners. Carried by the carriageframe formed by the opposed channel members 43 is an additional pair ofuprights 52 arranged in spaced relation from the uprights 49 and saiduprights are reinforced by triangular plates 53 likewise welded inplace.

Secured* to the other end of the carriage frame is a pair of uprightframe members 55 for supporting transverse channel members 56, andmounted on said channel members is a pair of spaced grooved rollers 57supported in journal housings 58 secured to the transverse channelmembers 56. All of the frame parts of the carriage structure are eitherwelded together or secured by threaded fasteners.

The upright carriage frame members 49 and 52 are arranged in spacedapart sets with the pair of uprights 49 connected by an angle bar 60 andthe uprights 52 connected by a similar angle bar 61. Spaced journalhousings 63 are mounted on the angle bar 60 in spaced apart relation andsimilar journal housings 64 are supported on the angle bar 61 with theiraxis corresponding to that of the journal housings 63.

Supported by the journal housings 63 and 64 is a pair of rotary shafts66 of tubular section and suitable thrust washers 68 are provided on theshafts to prevent endwise movement. The shafts 66 extend through the endwall plate 35 of the furnace housing and project a considerable distanceinwardly as shown in FIGURE 1. The inner ends of the shafts 66 areprovided with rollers 70 secured in place by washers 71.

The retort generally designated 6 includes a cylindrical shell 72 havinga reduced end portion 73 supported in a bearing structure which includesa collar '75 rigidly attached to the reduced end 73 of the retort whichis supported by the spaced grooved rollers 57. The other end of theretort shell 72 is partially closed by a gate or baflle wall 78 formingan opening '79 (FIG. 3). rI'he inner end of the retort shell isrotatably supported on the rollers 70 mounted on the inner ends of theshaft 66.

Formed internally and extending longitudinally of the retort shell 72 isa rib 3@ adapted to engage the workpieces during oscillation of theretort shell about its axis to thereby tumble the workpieces and presentdifferent surfaces to the carburizing atmosphere.

Mounted on the feed or reduced end 73 of the retort shell 72 is thecollar 8i? of a sprocket wheel 81 which is adapted to be driven by anelectric motor 82 connected to an oscillating drive unit S3 of the typeshown in United States Patent 2,887,887, issued to lennings, May 26,1959. The oscillating drive unit is provided with a control lever 84which may be manually operated to drive the output shaft and sprocketwheel S6 through an oscillatory arc of 180. The sprocket wheel 86 isconnected to the sprocket Wheel 81 by means of a sprocket chain 37 sothat when the manual control lever 84 is in one of its positions ofadjustment the retort shell 72 will be oscillated to and fro about itsaxis on each side of a vertical plane through the axis. In anotherposition or the manual control lever 84 the motor 82 which may beconnected to a suitable source of electrical energy will rotate theretort shell 72 continuously about its axis. This arrangement isnecessary to rotate the retort shell 72 to a position shown in FIGURE 3so that when the furnace is used as at for instance a batch type, thegate 78 will be displaced from a normally lower position or one reversedfrom that shown in FIGURE 3 and permit the opening '79 to allow theworkpieces to pass therethrough when the frame 7 is reciprocated todischarge the workpieces.

The frame structure 7 and the retort shell are reciprocated by means ofa mechanical motion device including drive linkage driven by an electricmotor 38. The armature shaft Iof the electric motor is provided with asuitable sprocket wheel over which is trained a sprocket chain 92 whichdrives a similar sprocket wheel afxed to one end of the shaft 94journaled in suitable openings in the mechanical motion housing 97. Acam (not shown) is secured to the shaft 94 and engages one end of areciprocating rod 96 slidably mounted in the bearing 97 The other end ofthe reciprocating rod 96 is pivoted as at 98 to a lever 10i). The lever164) is pivoted as at 161 to a bracket 74 attached to the framestructure and the upper end of the lever is connected to a link 101' bymeans of a pivot pin 102 and the other end of the link is connected toone of the cross members 44 of the reciprocating frame by means of apivot pin 105.

The electric motor 88 is of the variable speed type similar to the motor82 and is connected to a suitable source of electrical energy controlledby a rheostat in circuit with the motor to permit the speed thereof tobe regulated and thus increase or decrease the reciprocating rate of thecarriage 7. The stroke of the carriage and shell can be regulated byadjusting the pivot pin 101 in suitable openings therein (not shown).

Supported by the plate 51 is an L-shaped tubular fitting 106 having anenlarged end portion 107 adapted to receive the feed end or reducedportion 73 of the retort shell. The enlarged end 107 is formed of asuitable heat and Wear resisting metal alloy so that the portion inabutting relation with the reduced end 73 of the retort shell will notbe excessively Worn. An annular flange 103 is fitted on the L-shapedtubular member 106 and secured in place by Welding in any approvedfashion.

Guide rods having threaded end portions 109 extend through suitableopenings in the flanged plate 108 and the guide rods are threaded at oneend as at 110 to receive retaining nuts 111 arranged on opposite sidesof the plate 51. Abutment members 112 are threaded on the threadedportion of the guide rods and coil springs 113 are received on the rodswith one end engaging the abutment member 112 and the other end engagingthe flange plate 108. The L-shaped tubular fitting 106 is shaped toprovide a hopper 115 into which the workpieces are deposited andeventually fed to the retort shell 72 through the reduced tubularportion 73.

The other end of the retort shell 72 is engaged by a drum-shaped housing116 which is formed with annular wall 117 formed to provide a dischargepipe 118 having a discharge opening 119. The cylindrical wall 117 hasits open end enlarged as at 119 to receive the end of the shell 72 andabut the cylindrical portion 117. The drumshaped housing 115 is formedwith a plurality of circumferentially spaced bearing bosses 120 toreceive the ends of guide rods 126 which extend through suitable alignedopenings in the firebrick wall 37 and the end wall furnace plate 35. Theouter ends of the guide rods 126 extend through openings in a plate 130secured to one set of spaced apart uprights 52 on the reciprocatingframe. The guide rods 120 have their threaded end portions 132projecting through a similar plate 133 supported by the other set ofuprights 49 on the reciprocating frame member. The guide rods 120 areretained against displacement by nuts 135 received on the threaded ends132 of the rods. Coil springs 136 encircle the guide rods and have oneof their ends in abutting relation with the plate 133, while their otherends are engaged by an abutment washer 137 held in place by suitablethreaded fasteners or nuts 138. Thus, it will be seen, thatreciprocation of the frame 7 will also reciprocate the retort shell 6,and the retort shell is held against displacement on the carriage by theannular member 7 5 being engaged by the set of grooved rollers 57supported by the bearing housings 58.

Secured to the frame structure in an approved fashion is a water feedpipe 140 to supply coolant to the shafts 66. The Water is fed to theshafts 66 which passes toward the inner end thereof and then returns tothe outer end of the shafts 66 where it is discharged by gravity.

The discharge fitting or drum 116 has its discharge pipe 118 extendingthrough an elongated opening 150 in the lower furnace housing section 14and terminates in a flange 151. Secured to the flange is a dischargepipe 152 which is also hanged as at 153 to mate with the flange 151 andbe secured thereto by Welding or the like. The discharge pipe 152extends downwardly between spaced pairs of transverse carriage framemembers 44 and into a quench tank 155 disposed beneath the furnacestructure. A discharge conveyor 156 may be provided for removing theworkpieces or articles after the quenching operation.

Similarly, the conveyor 157 of the boot-type may be provided for feedingthe workpieces from a hopper 158 to a rotary metering device 159 whichhas its hopper 160 disposed to receive the workpieces from the dischargeend of the boot conveyor 157 and discharge the same through the outlet161 to the hopper 115 of the L-shaped tting 106.

When the furnace is used in a cyclic fashion the workpieces are fed insequence to the hopper and pass through the retort shell 72 uponenergization of the motors S2 and 88 to simultaneously reciprocate andoscillate the retort shell. When the workpieces reach the opposite endadjacent the discharge drum 116 they are permitted to fall through theopenings formed below the gate 78 and pass through the discharge tube113 and into the quenching tank Where they are continuously removed bythe endless conveyor 156, it being understood that the retort shell 72is angularly displaced by manipulating the control lever Sd to positionthe shell and gate 78 as shown in FIGURE 3 before the control 84 isoperated to connect the oscillating mechanism with the sprocket 86 andimpart oscillatory movement to the retort as it is being reciprocated bythe cam drive linkage 815-93. When the furnace is operated as abatch-type the workpieces may be manually fed to the hopper 115 andconveyed through the retort shell by the reciprocating shuffle linkage93 while it is being oscillated by the oscillating drive unit 83.

During the batch cycle, the control lever S41- is manipulated to rotatethe retort 72 to a position of angular displacement approximately fromthat shown in FIG- URE 3 so that the gate 78 Will be in its lowermostposition. Then by reciprocating the frame by the electric motor 3S andoperating the control S4 to effect an oscillating drive of the sprocket86 the shell 72 will be oscillated during reciprocation thereof and theworkpieces will be fed through the retort shell 72 and will be retainedby the gate 78. After the cycle is completed the shell 72 may beangularly displaced 180 so that the gate 7h is now in the position shownin FIGURE 3. Upon continued reciprocation of the frame 7 the workpieceswill be discharged from the shell 72 and will pass through the dischargeduct 152 to the quenching tank 155. In order to accomplish the dischargecycle above, the motor S8 is energized while the motor 82 is arrested sothat the retort shell 72 Will be reciprocated in a manner similar to ashuflie hearth furnace.

It will thus be seen that during operation of the furnace for heattreating metallic workpieces that the retort shell 72 can be oscillatedat a predetermined amplitude by varying the speed of the motor 82, andsimilarly frequency rate of reciprocation of the frame 7 can becontrolled by varying the current supply to the motor 88 and adjustin gthe speed of the motor.

In some metallic workpieces it is desirable to tumble the same whilepassing through the retort at a rapid rate while feeding them to thedischarge end at a relatively slow speed, and it will be seen that byregulating the speed of the motors 82 and 88 that the tumbling and feedof workpieces traveling through the retort shell 72 will be nicelycontrolled and effect uniform heat treating of various workpieces whichare of uneven section and irregular shape.

The heat treating furnace embodies a retort shell which projects intothe furnace housing 5 through an opening in one of the end Walls and issupported adjacent the other end wall by the rollers 70. This structureprevents the escape of gases and is highly efficient. In addition, theretort is sealed at both ends against the intrusion of air or combustiongases by the members 106 and 117 which contactually engage and seal theends of the retort shell. The only openings necessary in the furnacehousing are indicated at 74 and the openings for accommodating thesupporting rods 120 and the roller supporting shafts 66. Thus, the shellis effectively sealed and gases may escape from the furnace housingthrough a suitable stack (not shown) when the burners are in operationAlso, it is pointed out that the retort shell may be rotated in onedirection by manipulating the control 4 and simultaneously the shell canbe reciprocated when both electric motors 82 and 88 are energized. It isnecessary to employ a plurality of yieldingly mounted rods 120 forsupporting the cylindrical head 117 so that 7 the same will not rotatewith the retort shell, and since the Weight of the shell is supported bythe rollers 7?, the rods 120 are not placed under a stress or strain.

What I claim is:

1. In a heat treating furnace for metal Workpieces, a stationary furnacehousing, a source of heat in said housing, a retort having a heattreating chamber extending through an end Wall of said housing, meansfor reciprocating said retort longitudinally Within said housing, andindependent means for oscillating said retort to and fro duringreciprocation thereof.

2. In a heat treating furnace for metal Workpieces, a stationary furnacehousing, a source of heat in said housing, a retort having a heattreating chamber movably mounted Within said housing, means forreciprocating said retort, means for oscillating said retortindependently of the first named means, and baiiie means at the end ofsaid retort to retard the iiow of workpieces moved through said retortby reciprocating shuie action.

3. In a heat treating furnace for metal Workpieces, a stationary furnacehousing, a reciprocating frame mounted adjacent said housing, a retortextending into said housing and supported adjacent its ends by saidframe longitudinally of the housing axis, means for reciprocating saidframe and independent means for osciliating said retort Within saidhousing during the reciprocation of said retort to control the feedingand tumbling rate of the Workpieces through said retort.

4, In a heat treating furnace for metal Workpieces, a stationary furnacehousing having end walls, a reciprocating frame mounted adjacent saidhousing, a retort rotatably supported at its ends by said frame andhaving one end extending into said housing and the other end extendingthrough an opening in one of said end walls, means for feedingWorkpieces to the external end of said retort, means for dischargingworlrpieces from the other end of said retort, means for reciprocatingsaid frame to reciprocate said retort Within said housing andindependent means for oscillating said retort to and fro about itslongitudinal axis duringreciprocation of said retort along the sameaxis.

5. In a heat treating furnace for metal Workpieces, a cylindricalhousing having end Walls, a reciprocating frame mounted adjacent saidhousing, a retort mounted in said housing with one end extending throughone of said end Walls, means on said reciprocating frame for supportingsaid retort to reciprocate with said frame, independent means foroscillating said retort about its longitudinal axis, means for feedingWorkpieces to one end of said retort, means for retarding Workpieces asthey travel toward the opposite end of said retort and discharge meansextending through said housing for said Work` pieces.

6. In a heat treating furnace, an elongated furnace housing having endWalls, a cylindrical retort mounted Cil.

in said housing and extending through one of the end Wails thereofproviding internal and external portions, a hopper fitting yieldinglyengaging the external end of said retort, a hopper attached to saidfitting, means for feeding Workpieces to said hopper, a closure caphaving a discharge opening frictionally engaging the internal end ofsaid retort, a discharge pipe extending through said housing andConnected to said discharge port, means for reciprocating said retort tofeed Workpieces from the external end to the internal end, andindependent means for osciliating said retort and tumble said Workpiecesduring reciprocation of said retort.

7. In a heat treating furnace for metallic Workpieces, a cylindricalfurnace housing having end Walls, an elongated cylindrical retortmounted in said housing with one end extending through an end wall insaid housing providing internal and external end portions, reciprocatingsupport means for the internal and external ends of said retort, rollerson said support means for rotatably supporting said retort, a chargingcap yieldingly engaging the external end of said retort, means forfeeding workpieces to said cap, a discharge cap yieldingly engaging theinternal end of said retort having a discharge opening, a discharge pipeextending through said furnace housing and connecting said opening,means for reciprocating said retort, and independent means forosciliating said retort about its longitudinal axis.

8. In a heat treating furnace for metal Workpieces, a cylindricalfurnace housing, a series of heating units projecting into said housingand extending tangentially, end walls for said housing, a reciprocatingframe adjacent said housing, a cylindrical retort mounted in saidhousing with one end projecting through an end Wall thereof, supportmeans at each end of said frame for said retort, a hopper cap yieldinglyengaging the external end of said retort, means for feeding workpiecesto said hopper cap, a discharge cap yieldingly engaging the internal endof said retort and having a discharge opening, a discharge pipeextending through said housing and connected to said discharge opening,a bailie Wall adjacent said discharge cap to retard the discharge ofWorkpieces, means for reciproeating said frame and retort in a directionlongitudinally of the retort axis, and independent means for oscillatingsaid retort about its longitudinal axis whereby the feeding rate andtumbling rate of the Workpieces can be separately varied.

References Cited in the file of this patent UNITED STATES PATENTS1,551,197 Krebs Aug. 25, 1925 1,671,546 Romph May 29, 1928 1,686,565Knapp Oct. 9, 1928 1,797,125 Braekelsberg Mar. 15, 1931 1,965,881 Clarket al. July 10, 1934

1. IN A HEAT TREATING FURNACE FOR METAL WORKPIECES, A STATIONARY FURNACEHOUSING, A SOURCE OF HEAT IN SAID HOUSING, A RETORT HAVING A HEATTREATING CHAMBER EXTENDING THROUGH AN END WALL OF SAID HOUSING, MEANSFOR RECIPROCATING SAID RETORT LONGITUDINALLY WITHIN SAID HOUSING, ANDINDEPENDENT MEANS FOR OSCILLATING SAID RETORT TO AND FRO DURINGRECIPROCATION THEREOF.